The invention relates to a material pickup device provided with feeder mechanism for an agricultural harvesting machine which comprises a hydraulic drive consisting of a motor and a pump for a feeder mechanism of the material pick-up device.
In particular, the material pickup device may be a cutter bar for a self-propelled combine harvester. For the purposes of driving a feed reel as the feeder mechanism for a cutter bar in a self-propelled combine harvester, a constant displacement gear pump has been used until now, this pump having to be designed to be large enough to supply the necessary quantity of oil to the reel motor at full load. When the power requirements are lower than for a full load, the excess quantity of oil, which is delivered by the gear pump but is not required by the reel motor, is returned directly to the tank via a feed control valve connected between the gear pump and the reel motor. Due to the fact that the gear pump must always deliver the maximum amount of oil needed by the reel motor even though this quantity of oil is only required on rare occasions, the efficiency level of this type of reel drive is very low. Another disadvantage resides in the fact that the oil flows freely back into the tank from the outlet side of the reel motor so that it is not possible to ensure proper oil circulation when there is a change in load. Furthermore, in the case of the known reel drive, there is the disadvantage that additional valves must be employed and controlled when reversing the reel.
The present invention is directed to overcoming one or more of the problems set forth above.
An aspect of the present invention is to design the hydraulic drive for a feeder mechanism of a material pickup device in an agricultural harvesting machine such as to ensure the provision of a highly efficient, stable, oil circulation system which is easily reversible without involving additional expenditure.
Another aspect of this invention is for the drive pump for the motor of the feeder mechanism is a hydraulic pump whose delivery rate is adjustable in a continuous manner by means of a control lever, and in that the hydraulic pump and the motor of the feeder mechanism operate in a closed oil circulating system. With a drive for the feeder mechanism constructed in this manner, the hydraulic pump delivers just that quantity of oil, which the motor needs for its instantaneous operation. Moreover, it is ensured that the circulation of the oil is stable due to the functioning of the closed oil circulating system.
Yet another aspect of the invention envisages that a first line should lead to the inlet side of the hydraulic pump from a line connected to the low-pressure side of the hydrostatic drive for the vehicle and that another line should lead therefrom to the outlet side of the hydraulic pump, said first line and said other line each incorporating a respective non-return valve which blocks the return flow of oil from the hydraulic pump to the line which is connected to the hydrostatic drive for the vehicle. By virtue of such an arrangement, it is ensured that any lack of oil in the closed operational circulation system for the hydraulic pump and the motor is always replaced.
Still another aspect of the invention is a tank line incorporating a scavenger valve is branched off from that particular line leading from the motor to the hydraulic pump which forms the return line during the normal material feed operation. By virtue of such a known scavenger valve, it is ensured that a certain amount of oil can always flow into the tank from the closed oil circulating system and that this quantity will be replaced by fresh oil, namely, by the arrangement which was described in more detail in the following Paragraph:
During a reversing process, the feeder mechanism is driven at lower rotational speeds, from which it follows that the hydraulic pump must be set such that it will only deliver a small flow of oil. However, since a scavenger valve is employed during the reversing process in the line leading from the hydraulic pump to the motor, there is a danger that too large a quantity of oil will be branched off through the scavenger valve and fed into the tank so that there will be too little oil available for operating the motor correctly. In order to prevent this situation, the invention proposes that the scavenger valve be blocked during the reversal of the feeder mechanism, for example, for the purposes of removing a blockage of material, namely, by means of the pressurized oil itself which is flowing from the hydraulic pump to the motor. Naturally, during the reversal process, it is always possible to increase the rotational speed of the feeder mechanism so as to accelerate the clearance of the cutter plate with the help of the feeder mechanism.
Still another aspect of this invention is to actuate the control lever of the hydraulic pump by means of a linear drive, for example a piston-cylinder unit, via a 3/3-way valve in such a manner that the control lever is adjustable from a neutral position merely to one side. For the purposes of reversing, it is then only necessary to reverse the direction of rotation of the hydraulic pump.
The above aspects are merely illustrative of some of the numerous aspects associated with this invention and should not be construed as all-inclusive.